The present invention relates to a method and apparatus for determining the properties of a fluid traversing through a container or pipe. More particularly, the present invention relates to such a method and apparatus for non-invasively determining such fluid properties as density and viscosity using sonic energy propagated into the fluid to determine sonic propagation velocity of the sonic energy in the fluid in the container or pipe. The determined sonic propagation velocity can then be used as a "signature" along with fluid temperature to determine the fluid properties such as density and viscosity. Additionally, if the fluid identity is known, the pressure can also be determined. Furthermore, if the user has advance knowledge of the types of fluids conveyed in the pipeline, the fluid identity from amongst the possible fluids carried in the pipeline may be determined.
Systems are known which utilize the propagation of sonic energy through a container containing a fluid medium in order to determine the pressure of the fluid medium. For example, U.S. Pat. No. 3,977,252 to Krilova discloses a system for measuring liquid pressure in pipelines. This system is contactless and sends an ultrasonic pulse through the liquid, determines the rate of propagation of the pulse through the liquid and then determines the pressure of the liquid as a function of the propagation rate.
U.S. Pat. No. 3,942,381 to Brown discloses a clamp-on type transducer for measuring the time taken for an echo to travel through a pressurized bottle and for thereby determining the pressure of gas within the bottle.
U.S. Pat. No. 3,859,846 to Asada discloses a system with ultrasonic wave transmitting and receiving elements for locating an interface between different liquids flowing through a pipeline.
To applicant's knowledge, there is not, however, a system for determining the properties of a fluid present in a container, for example, the density and viscosity of a fluid in a pipeline, based upon non-invasive determination of sonic propagation velocity and fluid temperature, or which allows the determination, based upon advance knowledge of the types of fluids carried by the pipeline, of the fluid type from amongst several types. Furthermore, the invention provides a method based upon a knowledge of the fluid type, of determining the pressure of the fluid.